1. Field of the Invention
The present invention is directed to a cover plate assembly for wall-mounted electrical wiring devices, and more particularly to such assembly including a plate frame surrounding a wall opening and a face plate placed over the plate frame.
2. Description of the Prior Art
In the prior cover plate assembly, it is usual to use a plate frame for surrounding a wall opening in which one or more electrical wiring devices such as switches are installed and a face plate placed over the plate frame to conceal therebehind the plate frame as well as a mount bracket of the wiring devices while exposing through a center opening of the face plate only an operating portion such as an operator handle of the wiring device. The face plate is normally made from a plastic material as it is easy to have a decorative finish and is economical to manufacture. In such a prior art assembly, a problem arises when the center opening of the face plate is occupied fully by an operator handle of the wiring device. The problem is that the operator handle may be jammed due to dimensional instability of the center opening resulting from warp or deflection which is very likely in the face plate of plastic material. To overcome the problem, it has been a general practice to strengthen the face plate by the use of a backing or under plate which is made from a die cast material. However, such die cast under plate requires an extra trimming work to remove unacceptable burrs and therefore adds an extra manufacturing cost to the cover plate assembly.